Current Account Owner From SCD Type 2

SQL practice question · Hard · Subqueries & CTEs · Salesforce

account_owner_hist is a slowly changing dimension (type 2). An open (current) row has valid_to NULL or valid_to = '9999-12-31' (two loaders used different conventions). Because of a load bug an account can have more than one open row; then the open row with the latest valid_from is the current one. Accounts whose rows are all closed have no current owner and are excluded; history for accounts that are not in accounts is ignored. Return account_id, account_name, current_owner and owner_since (valid_from of the current row). Order by account_id.

Table: accounts

Schema of accounts
ColumnType
account_idINTEGER
account_nameTEXT
regionTEXT
Sample rows of accounts
account_idaccount_nameregion
1Acme CorpNA
2Bluefin LtdEMEA
3Cobalt IncAPAC
4Dune MediaNA
5Echo LabsAPAC

Table: account_owner_hist

Schema of account_owner_hist
ColumnType
account_idINTEGER
owner_nameTEXT
valid_fromDATE
valid_toDATE
Sample rows of account_owner_hist
account_idowner_namevalid_fromvalid_to
1Ravi2024-01-012025-03-31
1Meera2025-04-01NULL
2John2024-06-012025-12-31
2Aisha2026-01-01NULL
3Li2025-02-01NULL
5Raj2024-01-012025-01-31
Expected output on the sample data
account_idaccount_namecurrent_ownerowner_since
1Acme CorpMeera2025-04-01
2Bluefin LtdAisha2026-01-01
3Cobalt IncLi2025-02-01

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